1. Field of the Invention
The present invention relates to a fluid machine with scrolls, which is effectively employed in particular as an air-compressor under a low or medium pressure.
2. Discussion of Background
In recent years, fluid machines with scrolls have utilized in many industrial fields accompanied with the growth of the finishing machines, since scroll mechanisms have excellent characteristics in compression such as a small torque fluctuation and noises. However, fluid machines of low contents are mainly on the market, and there are processing problems on scrolls for manufacturing large machines, more specifically it is difficult to maintain the accuracy of scrolls.
In order to prepare fluid machines with scrolls which give large discharges, it is necessary to increase the widths of scrolls and eccentricities thereof. In addition to the above, in the case of fluid machines with scrolls which are driven at high speeds to be manufactured, it is necessary to completely keep its dynamic balance, and to reduce the generation of a shake and noises.
FIG. 6 shows a conventional fluid machine with scrolls. The conventional fluid machine has the shortcomings that it is not impossible to increase the scroll width H nor the eccentricity S thereof since a satisfactory orbiting accuracy cannot be obtained by the machine in which the radial load applied to the scrolls is received by a single side bearing.
A orbiting scroll 4 is supported by an eccentric driving shaft 5b by way of a bearing 9, and performs an orbiting motion as opposed to a fixed scroll 3. The centrifugal force F works on the orbiting scroll 4 at the center of gravity thereof when the scroll 4 orbits. Therefore, the centrifugal force F changes its direction as the result of the orbiting motion, thereby causing a shake. In the case where the center of gravity of the orbiting scroll to which centrifugal force is applied is not on the center line of the eccentric driving shaft 5b in the thrust direction thereof, it becomes extremely difficult to keep balance, since the centrifugal force F changes its size as the result from the orbiting motion. In addition, if the eccentricity S and/or the scroll width H are increased, the centrifugal force F becomes much larger, whereby an excessive shake is to be caused.